uscreditcards101-img-data-options.js

// https://www.uscreditcards101.com/wp-content/cache/autoptimize/js/autoptimize_9a2cfd2fee7b6b64b5fa19e57f03bc6c.js 
// https://www.uscreditcards101.com/how-to-use-plastiq-bill-pay/  
// https://www.v2ex.com/t/752795#reply113
$(document).ready(function () {
  setTimeout(function () {
    var observer = new IntersectionObserver(
      function (entries, observer) {
        entries.forEach(function (entry) {
          if (!entry.isIntersecting) return;
          var options = JSON.parse(entry.target.getAttribute("data-options"));
          var containerWidth = entry.target.offsetWidth;
          var url = options[0][1];
          for (var i = 1; i < options.length; i++) {
            if (containerWidth >= options[i][0]) url = options[i][1];
          }

          var xhr = new XMLHttpRequest();
          xhr.responseType = "arraybuffer";
          xhr.onload = function () {
            var blb = new Blob([xhr.response], { type: "image" });
            var bloburl = (window.URL || window.webkitURL).createObjectURL(blb);
            entry.target.src = bloburl;
          };

          xhr.open("GET", url);
          xhr.send();
          observer.unobserve(entry.target);
        });
      },
      { rootMargin: "300px 0px 300px 0px" }
    );
    document.querySelectorAll("img[data-options]").forEach(function (elem) {
      observer.observe(elem);
    });
  }, 0);
});